Project Summary/Abstract Opioid overdoses increased dramatically between 1999 and 2010. In 2010, 16,651 deaths were caused by a prescription opioid overdose, representing nearly 60% of all drug overdose deaths, and exceeding overdose deaths from heroin and cocaine combined. Recent modest declines in prescription opioid mortality rates have been paired with large increases in heroin abuse. In 2014, there were over 13,000 deaths involving heroin. In response to these trends, numerous federal and state policies have been adopted to curb the overdose rate. Improving access to naloxone through policy is especially promising as naloxone is known to be effective in reversing the life-threatening effects of opioids. Until relatively recently, however, naloxone has had a rather limited distribution network, followed by a recent wave of policy reforms motivated to improve naloxone access. The ability of policy to encourage additional naloxone access and subsequently reduce overdoses is generally unknown. In this project, we propose to study the ability of state policy to improve naloxone access and to understand which types of policies, if any, do so most effectively. We have preliminary evidence that permitting prescribers to dispense naloxone under their own authority is crucial for increasing naloxone prescribing. We will also place special emphasis on the responses of private pharmacies to state policies which legalize dispensing of naloxone without a patient- specific prescription. Large pharmacy chains have enacted their own private policies to improve naloxone access, and these policies have spread over time across several states. The effects of these private policies should vary geographically based the penetration of these chains in different communities. We will study whether private pharmacy policy can improve access and reduce overdoses above and beyond state policy. We will use a variety of rich data sets to measure our outcomes. We will use comprehensive quarterly zip code-level data on naloxone dispensing for 2010-2017. We will also collect data on pharmacy locations as well as pharmacy-level policy concerning naloxone dispensing. We will explore what types of state policy improve naloxone access and the role of pharmacy policy. We will subsequently test whether improved naloxone access affects fatal overdoses and nonfatal overdoses This project will present some of the first evidence of the effectiveness of naloxone policy on naloxone prescriptions while also exploring the mechanisms which make such policies most effective in terms of dispensing and reducing overdoses.